Add support for SPARQL prefix syntax in Turtle files

[rjyounes]

Turtle allows SPARQL prefix declaration syntax:

The Turtle language originally permitted only the syntax including the '@' character for writing prefix and base directives. The case-insensitive 'PREFIX' and 'BASE' forms were added to align Turtle's syntax with that of SPARQL. It is advisable to serialize RDF using the '@Prefix' and '@base' forms until RDF 1.1 Turtle parsers are widely deployed.

• https://www.w3.org/TR/turtle/

Currently the serializer converts the SPARQL syntax back to Turtle. Could you let it pass through instead - or at least as an option?

[mereolog]

@rjyounes the recommendation you quote comes from 2014. In https://www.w3.org/TR/rdf12-turtle/ from Feb 2025 this note is rephrased so that this recommendation is no longer emphasized. Is there a specific use case that you have in mind here?

@ElisaKendall , @przemekgradzki , @wsobel , @jziemer2 , @dallemang may I have your view on this?

[rjyounes]

@mereolog Indeed, the latest Turtle spec no longer advises against using the SPARQL syntax, therefore the request for the serializer to support the SPARQL prefix syntax makes even more sense. The point is that currently the serializer is converting this syntax back to the original @prefix syntax instead of letting it pass through.

[rjyounes]

@mereolog Maybe I didn't make the request clear: the Turtle spec allows the SPARQL prefix declaration syntax, but the serializer converts it back to the original Turtle @ syntax. We want to use the SPARQL syntax in our Turtle files so that it's easier to copy and paste between Turtle and SPARQL. So the ask is that the serializer allow that syntax to pass through.